10.6084/m9.figshare.4665046.v1
Salas C.A.
Salas
C.A.
Yopak K.E.
Yopak
K.E.
Lisney T.J.
Lisney
T.J.
Potter I.C.
Potter
I.C.
Collin S.P.
Collin
S.P.
Supplementary Material for: The Central Nervous System of Jawless Vertebrates: Encephalization in Lampreys and Hagfishes
Karger Publishers
2017
Agnathan
Petromyzontiformes
Myxiniformes
Brain size
Life cycle
Lifestyle
Feeding behavior
Activity
Evolution
2017-02-17 11:06:34
Dataset
https://karger.figshare.com/articles/dataset/Supplementary_Material_for_The_Central_Nervous_System_of_Jawless_Vertebrates_Encephalization_in_Lampreys_and_Hagfishes/4665046
<p>Lampreys and hagfishes are the sole surviving representatives of the
early agnathan (jawless) stage in vertebrate evolution, which has
previously been regarded as the least encephalized group of all
vertebrates. Very little is known, however, about the extent of
interspecific variation in relative brain size in these fishes, as
previous studies have focused on only a few species, even though
lampreys exhibit a variety of life history traits. While some species
are parasitic as adults, with varying feeding behaviors, others
(nonparasitic species) do not feed after completing their macrophagous
freshwater larval phase. In addition, some parasitic species remain in
freshwater, while others undergo an anadromous migration. On the basis
of data for postmetamorphic individuals representing approximately 40%
of all lamprey species, with representatives from each of the three
families, the aforementioned differences in life history traits are
reflected in variations in relative brain size. Across all lampreys,
brain mass increases with body mass with a scaling factor or slope (α)
of 0.35, which is less than those calculated for different groups of
gnathostomatous (jawed) vertebrates (α = 0.43-0.62). When parasitic and
nonparasitic species are analyzed separately, with phylogeny taken into
account, the scaling factors of both groups (parasitic α = 0.43,
nonparasitic α = 0.45) approach those of gnathostomes. The relative
brain size in fully grown adults of parasitic species is, however, less
than that of the adults of nonparasitic species, paralleling differences
between fully grown adults and recently metamorphosed individuals of
anadromous species. The average degree of encephalization is found in
anadromous parasitic lampreys and might thus represent the ancestral
condition for extant lampreys. These results suggest that the degree of
encephalization in lampreys varies according to both life history traits
and phylogenetic relationships.</p>